(19) |
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(11) |
EP 0 911 619 A3 |
(12) |
EUROPEAN PATENT APPLICATION |
(88) |
Date of publication A3: |
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26.04.2000 Bulletin 2000/17 |
(43) |
Date of publication A2: |
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28.04.1999 Bulletin 1999/17 |
(22) |
Date of filing: 11.09.1998 |
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(51) |
International Patent Classification (IPC)7: G01J 1/00 |
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(84) |
Designated Contracting States: |
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AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE |
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Designated Extension States: |
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AL LT LV MK RO SI |
(30) |
Priority: |
12.09.1997 JP 24882397 12.09.1997 JP 24882497
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(71) |
Applicants: |
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- Meiryo Tekunika Kabushiki Kaisha
Nagoya-shi, Aichi-ken (JP)
- Sato, Susumu
Akita-shi, Akita-ken (JP)
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(72) |
Inventors: |
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- Sato, Susumu
Akita-shi, Akita-ken (JP)
- Zhou, Ying
Bedford Hills, NY 10507 (US)
- He, Zhan
Bedford Hills, NY 10507 (US)
- Togashi, Yoshihiro
Kasugai-shi, Aichi-ken (JP)
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(74) |
Representative: Bannerman, David Gardner et al |
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Withers & Rogers, Goldings House, 2 Hays Lane London SE1 2HW London SE1 2HW (GB) |
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(54) |
Methods and apparatus for detecting liquid crystal display parameters using stokes
parameters |
(57) A polarizing plate 4 is disposed to polarize light parallel to the X axis of liquid
crystal display 3, which may be optionally rotated to a position where the intensity
of a light that transmits the liquid crystal display 3 takes an extreme value (maximum
or minimum) and an output Ix using a photodetector 6 is measured. The polarizing plate
4 is then disposed to polarize light parallel to the Y axis to thereby measure an
output Iy using the photodetector 6. The polarizing plate 4 is then disposed to polarize
the light in the direction inclined by 45 degrees between the X and Y axes to thereby
measure an output I45 using the photodetector 6. A quarter wavelength plate 5 optionally
may be disposed between the polarizing plate 4 and the liquid crystal display 3 such
that its axial direction is inclined by 45 degrees from the polarizing direction of
the polarizing plate 4 while disposing the polarizing plate 4 so as to polarize light
at 45 degrees from both the X and Y axes. In this position, an output Iq45 is measured
by the photodetector. Stokes parameters are calculated according to each of the measured
values Ix, Iy, I45 and Iq45, and according to the calculated Stokes parameters, the
thickness of the liquid crystal layer and/or the twist angle of liquid crystal molecules
of the liquid crystal display 3 can be determined. Optionally, the light intensities
may be measured by a two-dimensional photodetector and Stokes parameters for a plurality
of points on the liquid crystal display may be simultaneously or substantially simultaneously
determined.

